Earlier this week, an anonymous source appeared on Australian radio station 6PR, claiming AC/DC are on the verge of retirement due to the ill health rhythm guitarist Malcolm Young.

While Billboard reports today (April 16) that sources close to the band say rumours of the band calling it quits are "exaggerated", Choirboys frontman Mark Gable, who is friends with AC/DC's Malcolm and Angus Young, says that the guitarist is seriously ill and will not be able to perform any more.

"From what I understand, and it's even been confirmed in part by his son Ross, it would appear Malcolm is unable to perform any more," he told Australia's ABC Radio. "It's not just that he is unwell, it's that it is quite serious. It will constitute that he definitely won't be able to perform live… He will probably not be able to record."

Earlier this year, the band talked about recording a new album and playing an extensive tour to mark their 40th anniversary, revealing plans to enter the studio later this year in order to record their first new album since 2008's Brendan O'Brien-produced 'Black Ice'.

Gable claims this could go ahead without Malcolm Young, who could be replaced by his nephew Stevie. "There was speculation that they had this even tacit agreement that if no member currently was able to perform, DC would cease," gable said. "However, Alex Young's son Stevie replaced Malcolm Young a few years back for a tour, and nobody knew the difference."

The retirement rumours earlier this week were initially contradicted by reports in The Australian newspaper saying that AC/DC have studio time booked in Vancouver from May 1.

Earlier this year, Brian Johnson said: "Its been 40 years of the band's existence. So I think we're gonna try to do 40 gigs, 40 shows, to thank the fans for their undying loyalty. I mean, honestly, our fans are just the best in the world, and we appreciate every one of them. So, like I said, we'll have to go out, even though we're getting a bit long in the tooth. You know what? It's been four years, and I'm really looking forward to it."